< 74t ) 
trodudDgdifpofidans in the matter, he intentionally works i 
and, as fometimes he gives that weight to the matter, not en- 
dowing it with a principle of life, fo be often difpofes it to re- 
ceive life and introduces itrwhich Pofition I conceive will hold 
good^notwithftanding fomelate induftrious eflTays to prove that 
there is no Equivocal birth. 
Thus,Si>,I have informed you,that ih^trochites are parts of 
Rock-plants, and have given you fomething of what I conceive 
and praftically know concerning their vegetation^ effaying 
withal to render fome account of thofe various figures which are 
found amongft Minerals: Not but my thoughts are very poor of 
thefe £hings,which can make but a very flender addicion to that 
rich (lore fcnt you by your learned Correfpondents^ I fliall 
conclude with a requeft to you concerning a thing, which may 
prove very much to the advantage of thofe who are concerned 
in Mineral adventures: Ic is a conftant opinion amongft our 
Miners,that Lead'OAr di^cov^vs it felf by anOily-fmell,and that 
chiefly in a morning a little before the rifing of the Sun, efpeci- 
ally when fome fliow'rs have fall'n in the night : This being fo,I 
find two things in the tra»fa£f, which give me hopes that this 
way of difcovery may bemuch improved by Art: The firjl\s 
an inximation of a way fliewn by Sr. William Petty in his Trad 
of Double proportions ^v^hettby we may difcover a fnvell at a great 
diftance,and foconfequently the intenrnefs and remifnefsof it 
nearat hand, wherein the chief difficulty will confift; for,where 
thefe Smells rife,they commonly diffufe themfclves to a furlongs 
circumference or more, fo chat we are more at a lofs to find ex- 
adly the place whence they rife, than to make a firft difcovery 
of them. The fecond thing is the Statical Barofcope of Mx.Bo^le^ 
which I conceive may give us fome light af their true fource^ 
there being probably at that place a confiderable variation in 
the preffure of the Atmofphere by reafon of the Mineral-fteams 
which are there in thegreateft abundance, I am not ignoranr,thac 
fomeftrongly fermented beds of Mineral-earths and rufts, which 
are fometimes barren, fend forth a ranker imell than Oar it felf, 
which may now and then deceive us 5 but becaufe for the moft 
part thefe are concomitants of Oar, we may not look upon the 
attempt as fruitlefs* Now,S/>^my humble requeft to you is, that 
you will be pleafed to oblige me with your opinion of the pro- 
bability ofchefuccefs,and to inftru^i me iti the way which Sr, 
William 
